Beating process and apparatus for practising same



May 24, 1932. G. A. RICHTER ET AL BEATING PROCESS AND APPARATUS FOR PRACTISING SAME Filed Oct. 6, 1927 3 Sheets-Sheet 1 y 1932- G. A. RICHTER ET AL 9,

HEATING PROCESS AND APPARATUS FOR PRACTISING SAME Filed Oct. 6. 1927 3 ShfiGts-Sheet 2 y 24, 1932- cs. A. RICHTER ET AL 1,859,890

SEATING PROCESS AND APPARATUS FOR PRACTISING SAME Filed Oct. 6. 1927 3 Sheets-Sheet 3 Patented May 24, 1932 UNITED STATES PATENT OFFICE GEORGE A. RICHTER AND MILTON O. SCHUR, OF BERLIN, NEW HAMPSHIRE, ASSIGNORS TOIBROWN COMPANY, OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE BEA'I'ING PROCESS AND APPARATUS FOR PRACTISING SAME Application filed October 6, 1927. Serial No. 224,427.

This invention relates to the beating of cellulose fiber, being especially intended to provide a process of beating and apparatus for practising the same, so that such fiber may be hydrated more satisfactorily, with the expenditure of less energy and in a shorter period of time, than was heretofore possible. When cellulose fiber is beaten, it assumes a gelatinous character and is said to become hydrated. Vhen the beaten fiber is run off into paper, the gelatinized cellulose sets or hardens during drying, serving to bond together the individual fibers and thus to impart strength to the finished paper. In certain special instances fiber is beaten until it is completely or very nearly completely gelatinized, for example, when hard paper board or translucent papers of the so-called glassine variety are desired.

The beating of cellulose fiber to effect gelatinization is generally practised in a hollander or beater engine equipped with a beater roll and bed-plate. As the beater roll rotates, the fibers are worked against each other and against the bed-plate, becoming thereby frayed and shortened and converted in gradually increasing measure into fibrillae of which the individual fibers appear to be largely or perhaps entirely composed. These changes become manifest in an enhanced sliminess or gelatinization of the pulp mass and in an increased toughness, translucency, and compactness of paper prepared from the beaten fibers. During beating, the temperature of the beater charge rises, for the working of'thepulp and the friction of the roll against the charge and against he bed-plate are in v fact mostly converted into heat. Assuming complete conversion into heat, that the beater charge consists of 1000 pounds of fiber and 20,000 pounds of water, and that energy is being expended at the rate of 75 horse-power, then since the specific heat of the beater charge is approximately 1, the temperature rise in the beater will be about 9 F per hour. Inasmuch as cellulosic fibers may require from four to twelve hours beating or even higher, it will be seen that a beater charge may become quite warm or even hot as beating continues. This is, in fact, the case, for some grades of kraft fiber which require about eight or nine hours beating prior to paper formation rise materially in temperature as beating continues, and it is not uncommon to find that in the summer time, when room temperature is about 80 F the charge has risen to a temperature of 120 F., or reater, at the end of the beating period. here fiber is highly beaten, as in the manufacture of translucent papers, the temperature rise may even be greater.

In our research work performed in connection with heating, we have observed that it is much more diflicult to hydrate fiber at an elevated temperature than at room or lower temperatures. Thus, whereas about twelve hours beating in the ordinary way may be requlred to convert a certain type of fiber to a given high slowness as measured by the resistance of a pad of pulp under standardized conditions to the flow of Water through it, we have found that if the fiber is ma1n tained at room temperature or very close thereto, the time required to produce such slowness may be reduced to seven or eight hours. We have further found that if the temperature durin beating is revented from increasing, a etter grade 0 paper is produced. Beating at elevated temperature not only impedes gelatinization, but also causes a certain amount of pulverization of the fiber. The same slowness produced by beating at room or at lower temperature, on the other hand, results from the presence of a larger amount of elatinized cellulose and a smaller amount 0 pulverized fiber and hence the resulting paper is stronger. When fiber is'highly beaten, this condition becomes very clearly apparent. Thus, fiber beaten to a highly gelatinous condition at room or at lower temperature yields paper of greater translucency and clarity and of greater strength than similar fiber highly beaten to the same slowness at elevated tem eratures.

In accordance with the process of the present invention, cellulose fiber is beaten to the desired slownessv while maintained at room or at lower temperatures. This is accomplished during the beating operation by removing the heat generated by the roll. The removal of heat may be accomplished by various methods and means. For instance a cooling medium may be circulated through a hollow metallic lining in the walls, midfeather, and floor of the beater. This method, however, is inefiicient and difficult to perform, particularly when thick stock is being beaten, for the heat transfer through thick stock is very low. If the cooling medium is circulated under the bed-plate and backfall, better results are secured, heat transfer being higher at these places. Another method may consist in arranging cooling coils or cooling plates in the beater to cool the charge directly, but this would tend to impede free circulation of the stock. Still another method may consist in gradually addin cold water or ice to the charge as it is being eaten. This method, however, results in an undesirable dilution of the charge and when ice is used involves considerable expense. Dilution of the charge results in a greater consumption of power, as energy is expended in circulating more water than is necessary through the beater. In certain cases it may be expedient to use a hollow worm through which coolin water may be circulated. The worm woul be submerged in the stock and mechanically rotated so as to offer no resistance to the circulation of the pulp. Our preferred method of removing heat from the charge comprises continuously removing water or stock from the beater, preferably stock of lower fiber concentration than that being beaten, cooling the water or thin stock, and continuously returning it to the beater. By this method, the stock being beaten may be maintained at room or lower temperature, so that it takes much less time to beat to a given slowness and at the same time results in a stronger paper. Our process finds especial utility when a refractory fiber which requires a long beating period to be reduced to the desired slowness for paper formation is used as a raw material, or when fiber is being strongly beaten to a highly gelatinous condition so that temperatures of about 150 to 160 F. might be reached at the end of beating if provislon for removing heat during beating were not made.

An important advantage incident to our preferred method of removing heat during beating is, that it may be practised with usual beating equipment and involves a minimum expense. Thus, in practising this method, a beater equipped with the usual washing drum may be employed. To prevent clogging of the drum, it may be preferred to replace the usual wire gauze covering with metal plates having fine openings, say, .04 to .20 inches in diameter, so as to permit stock of low fiber concentration containing only short fibers, fiber fragments and gelatinized cellulose to pass into the drum. During beating, the washing drum is put in operation, and the water or stock of low fiber concentration passing thereinto is recovered and cooled as by passing through a cooling coil, whence the water or stock is returned to the beater.

With the foregoingand other objects in view, the invention consists in the novel feature of procedure, as well as of combinations and arrangements of parts, as will be morefully hereinafter described in conjunction with the accompanying drawings, wherein Figure 1 represents in perspective a beater of the usual type, in connection with which the present invention may be practised.

Figures 2 to 8, inclusive, represent somewhat diagrammatically and conventionall a section through the beater, each illustrating various apparatus with which the beater may be equipped in practising our invention.

Referring to the drawings, Figure 1 illustrates a beater of a well known type comprising a tub 1 having the usual midfeather 2, on one side of which operates a beater roll 3 and on the other side a washing drum 4. A washing drum covered with wire gauze as ordinarily would become clogged, as the fiber would mat thereon and the interstices in the mat would become plugged with gelatinized cellulose as beating progressed. Hence, as shown, we prefer to cover the periphery of the drum 4 with plating 5 having fine openings permitting passage of water and fiber in finely divided or hydrated condition into the drum. The drum shown is provided with internal, trough-shaped partitions 6, water and fiber passing into the drum being lifted by these partitions and then discharged into a hollow shaft 7, on which the drum is mounted, passing from the shaft through an outlet pipe 8. As indicated in Figure 2, the white-water passing into the pipe 8 is forced by a pump 9 through a cooler 10, which may, for instance, be of the double wall coil type and designed to permit passing a cooling medium into indirect countercurrent flow to the white-Water. The white-water passes from the cooler through a pipe 11, which returns it into the beater 12. By continuously withdrawing water or stock from the beater, cooling it, and then returning it to the beater, the beater charge may be maintained at a temperature permitting, as explained above, a given degree of gelatinization in a much shorter period of time than that usually necessary.

In practising the process of the present invention, the fiber employed as a raw material may be slushed with water in the beater to a 4% to 8% fiber concentration; The washing drum may be designed-to remove whitewater of, say, 2% fiber concentration from the stock during beating. Assuming that the beater charge consists of 1000 pounds of fiber at a stock density of 5% and that room temperature is 80 F., if 40 gallons of whitewater of 2% fiber concentration is removed from the beater per minute and cooled by a medium such as water from a temperature of 80 F. to F., and then returned to the beater, rise in temperature of stock in the beater will be prevented and at the end of about 7 or 8 hours the stock will have acquired a slowness equal to that usually produced in a 12-hour beating period. In addition, the

hydrated stock is of better papermaking character than stock beaten as ordinarily.

If the stock is converted to a pronounced gelatinous condition without provision for removing the generated heat, its temperature may go to 150 or 160 F., or even higher, at which temperatures hydration is slow and the quality of the stock impaired. If instead of permitting temperature increase the stock is maintained at a temperature of, say, F. in accordance with our process, the rate of hydration may be maintained high, so that the desired slowness of stock is reached in a much shorter period, while at the same time a better quality of beaten product results.

If fiber is beaten to a high degree of slowness, the stock may part with its water to ward the end of beating very slowly so that it may be advantageous to design the drum to handle more white water than is necessary to prevent temperature rise in the beater at the start of beating but of sufiicient capacity to maintain the stock in the beater at the desired temperature when elatinization has been highly developed. nasmuch as the pump 9 might fail to handle all the white water removed at the start of beating, the pipe 8 may advantageously be arranged to deliver into an open funnel 80 connected to the suction of pump 9, the funnel having an overflow pipe 81 delivering excess whitewater back into the beater.

To overcome any tendency of the pump to become underprimed as beating progresses, it may be piped up so as to operate at capacity at all times. Such an arrangement is shown in Figure 3 wherein the pump 9 forces the white water removed from the beater through a cooler 10 as previously described, and then, instead of discharging all the cool white water into the beater, passes some back through a pipe 13 into pump 9. With such an arrangement, if the supply of white water from the drum 5 is insufficient at any time to keep the pump 9 primed, the pump will withdraw some of the white water passed through the cooler and will recirculate it through the cooler, the remainder of the white water passing through a valved pipe 110 to the beater.

- It is sometimes possible to avoid the use of a pump, thereby reducing the cost of the equipment. This may be done by taking advantage of the fact that the white-water coming from the drum is at a higher level than that in the beater proper. This procedure is shown in Figure 4,'where the white-water passing from the washing drum into the outlet pipe 8 is allowed to gravitate through one or more coolers 16, thence through a pipe 17 into the beater.

It may be advantageous, in certain instances, to cool the white-Water a substantial amount,'say, from room temperature to the freezing point of Water. To this end, a refrigerant may be used in lieu of a cooling medium such as water at seasonable temperature. As shown in Figure 5, the whitewater is first cooled by passing it through a cooler 10, which may be supplied with water at seasonable temperature, and then through a second cooler 18, which may be supplied with cold water or brine. The cooled white water then passes to the beater througha pipe 19. Such a system may be used to maintain the stock being beaten below room temperature and may be advantageous, particularly in a mill manufacturing papers of theglassinevariety where translucency and clarity of paper are of prime importance, for heating at low temperature improves these characteristics.

Inasmuch as it'is often desirable that the stock be warm at the paper. machine, since drainage and removal of white water from the nascent paper web are thereby facilitated, permitting faster papermaking speed, it is evident that it might be desirable to increase the temperature of the stock after beating. Thus, beaten stock which is cold is sometimes heated to 100 F., or higher, to condition it for papermaking. Figure 6 illustrates a procedure which may be followed if it is desired to utilize heat removed from the stock being beaten. As shown in this Figure, the efliuent water fram the cooler 10, which has been raised in temperature by the stock coming from the beater, is passed by a pump 20 through a pipe 21 into a tank 22. The water in tank 22 is fed to the paper machine showers or is otherwise used in place of fresh water anywhere between the heater and the dryer.

In lieu of cooling both fiber and water removed from the beater, it may be desirable first to separate and recover as much fiber as possible from the water, and then to cool only the water. This procedure may be preferable where relatively large openings are used in the washing drum, this permitting stock of fairly high fiber concentration to be withdrawn from the beater. As shown in Figure 7 this is accomplished by first passing the stock through a fiber separator 25, which eifects a. separation of fiber from water, and then passing the water, together with any fiber or gelatinized cellulose which it may contain, through a cooler 26, and then through a pipe 27 to the beater. The separated stock may be returned through a pipe 28 to the beater. After beating has progressed for a considerable time, most of the fiber passing with the water into the washing drum will be in a well-hydrated condition, particularly if the fiber is being highly beaten. In such case, it may be desirable to effect a separation of the fiber from the water, recover it for papermaking, and add unbeaten fiber to the beater to make up for the fiber removed from the system. This operation may be carried out continuously, a certain amount of well-hydrated fiber being continuously removed from the system, and a corresponding amount of unbeaten fiber added to the beater. This procedure is illustrated in Figure 8, which shows the stock withdrawn from the beater passing through a separator 25, the separated, well-hydrated material passing through an outlet pipe 29, whereupon it may be recovered and utilized for paper manufacture. Fresh fiber may be added to the beater through a supply pipe 30 in amount corresponding to the wellhydrated material being withdrawn from the system. The water, together with any associated material, passes from the separator through a cooler and thence through a pipe 27 into the beater.

In the apparatus shown in Figures 7 and 8, if complete separation of fiber and water may be made, in lieu of cooling the water coming from the beater, fresh, cool water may be supplied to the beater. This procedure-may be followed at the start of beating, when the fiber is of long length and free, for little well hydrated material passes through the washing drum and into the cooling system, the fiber present in the water being substantially completely recoverable by a fiber separator. As beating progresses and the fiber becomes short and gelatinized, complete separation between fiber and water becomes more difficult, so that the water having fiber in it is preferably cooled and returned to the beater. When stock contains size, fillers, or other valuable materials, the water coming from the beater is cooled and returned to the beater, so as to avoid the loss of such materials.

Havin thus described certain embodiments 0 our invention, it is evident that change and modification might be made therein without departing from the spirit or scope of invention as defined in the appended claims.

WVhat we claim is:

1. A rocess which comprises beating cellulose fi er stock, removing a portion of the stock during heating, indirectly cooling such stock, and returning it to the stock being beaten.

2. A process which comprises beating cellulose fiber stock, continuously removing durlulose fiber stock, continuously removing water from such stock during beating, cooling such water, and'returning it to the stock being beaten.

4. A process which comprises beating cellulose fiber stock, continuously removing during beating a portion of the stock of lower fiber concentration than that being beaten, cooling such stock below room temperature, and returning it to the stock being beaten.

5. A process of paper manufacture which comprises beating cellulose fiber stock, passing a portion of the stock into indirect countercurrent flow with cooling water thereby cooling the stock and warming the water, and using the warm water in lieu of fresh water between the beater and the dryer.

6. A process which comprises beating cellulose fiber stock, removing a portion of the stock during beating, separating and recovering the fiber content of such stock, cooling and returning the water to the stock being beaten, and adding suflicient fresh stock to the stock being beaten to make up for the separated stock.

7. The combination with a beater engine, of means for removing stock from the beater, means for indirectly cooling said stock, and means for returning said cooled stock to the heater.

8. The combination with a beater engine, of means for removing from the beater stock at lower fiber concentration than in the beater, means for cooling such removed stock, and means for returning said cooled stock to the beater.

9. The combination with a beater engine, of means for removing from the beater stock at lower fiber concentration than that in the beater. means for cooling said stock a substantial amount, and means for returning said cooled stock to the beater.

10. The combination with a beater engine having a washing drum for removing stock of low fiber concentration from the beater, of means for cooling the removed stock, and means for returning the cooled stock to the beater.

11. The combination with a beater engine having a washing drum whose periphery is covered with perforated plating permitting the passage of stock of low fiber concentration thereinto, of a pump communicating with the stock passing into said drum, a cooler through which said stock is forced by said pump, and a pipe returning said stock from said cooler to said heater.

12. The combination with a heater engine having a washing drum whose periphery is covered with perforated plating permitting the passage of stock of low fiber concentration thereinto, of a. pump communicating with the stock passing into said drum, a

cooler external to said beater through which said stock is passed by said pump, means for returning stock from said cooler to said heater, and means for returning a portion of said stock to said pump.

13. The combination with a beater engine,

of means for removing water from the beater, means for indirectly cooling such wa ter, and means for returning said cooled water to the beater.

14. The combination with a beater engine,

of a washing drum which removes water from the beater and raises it above the level of the stock in said engine, and a cooler through which said removed water flows by gravity back into the beater.

15 A process which comprises beating a charge of cellulose fiber stock while at the same time removing a continuous stream from the charge, indirectly cooling the stream, and returning it to the charge being beaten.

16. A process which comprises beating cellulose fiber stock, passing a portion of the stock into the indirect countercurrent flow with a cooling medium, and returning said cooled portion to the stock being beaten.

17. The combination with a beater engine, of means for removing a continuous stream of material from the beater, means for passing a cooling medium into indirect countercurrent flow with said stream of material, and means for returning said stream of cooled material to the beater.

In testimony whereof we have aifixed our signatures.

GEORGE A. RICHTER.

MILTON O. SCHUR. 

